1. Field of the Invention
The present invention relates to an optical semiconductor device including a light emitting device and a photodetector, and more particularly to an optical semiconductor device as a chip-type photocoupler or as an optical integrated circuit device and a method of manufacturing the optical semiconductor device.
2. Description of the Related Art
Unexamined Japanese Patent Application KOKAI Publication No. H8-264823 discloses, for example, two types of conventional optical semiconductor devices, as chip-type photocouplers, each includes a light emitting device and a photodetector, which are mounted on a concaved-type resin substrate and are sealed with a translucent resin which is coated with a light-shielding resin. In such a conventional optical semiconductor device, light emitted from the light emitting device passes through the translucent resin, and reflected on the interface between the translucent resin and the light-shielding resin so as to be detected by the photodetector.
Another optical semiconductor device disclosed in the above patent publication includes the first concaved-type resin substrate, on which a light emitting device is mounted and sealed with a translucent resin, and the second concaved resin substrate, on which a photodetector is mounted and is sealed with a translucent resin. In this optical semiconductor device, the first and second concaved-type resin substrates are connected with and face each other so that a light emitting surface of a light emitting device faces the photodetection surface of the photodetector. The light emitted from the photodetector passes through the translucent resin filling both concaved-type resin substrates, and detected by the photodetector.
Disclosed in Unexamined Japanese Patent Application KOKAI Publication No. H7-303083 is an optical semiconductor device having the structure of an optical integrated circuit. In this optical semiconductor device, a light emitting device and a photodetector are mounted on a wiring substrate, and a transparent plate covers the wiring substrate. In the optical semiconductor device, the light emitted from the light emitting device is reflected on the transparent plate and detected by the photodetector.
As described above, one of the optical semiconductor devices, disclosed in Unexamined Japanese Patent Application KOKAI Publication No. H8-264823, includes the light emitting device and the photodetector sealed with the translucent resin which is coated with the light shielding resin. In this structure, if the interface between the translucent resin and the light-shielding resin is defective, the reflection direction of the light deviates from a desired direction, and the efficiency of the photodetection in the photodetector is low. In the structure where the light emitting device and the photodetector arc arranged on one plane, the area of the optical semiconductor device is large, thus optical semiconductor devices can not be mounted with high density.
In another optical semiconductor device, disclosed in Unexamined Japanese Patent Application KOKAI Publication No. H8-264823, wherein two concaved-type resin substrates are included, a physical interface exists between both concaved-type resin substrates filled with the translucent resin. In this structure, light is reflected on this interface and scattered in directions. As a result of this, the efficiency of the photodetection in the photodetector is low. In the case where both concaved-type resin substrates are not completely adhered to each other and air bubbles are generated in the interface therebetween, the withstanding voltage between the light emitting device and the photodetector is low, and the resistance of the device is also low.
Further, in the optical semiconductor device disclosed in Unexamined Japanese Patent Application KOKAI Publication No. H8-264823, the light emitting device and the photodetector are electrically connected with the substrate through bonding wires. In order to prevent the bonding wires from being broken down, the curvature of the loop needs to be low. As u result, the chip is made large in height. In the structure where the chip is made large in height, the optical path length between the light emitting device and the photodetector is large, and the translucent resin fills the space between the light emitting device and the photodetector, thus the light passing through the translucent resin is attenuated. In addition, scattering of the light occurs in the structure where the translucent resin fills the space between the two. Thus, the efficiency of the photodetection of the photodetector is low.
In the optical semiconductor device disclosed in Unexamined Japanese Patent Application KOKAI Publication No. H7-303083, the light emitting device and the photodetector are mounted on one plane. The area where to mount the photocoupler including the light emitting device and the photodetector is large, thus optical semiconductor devices can hardly be mounted with high density.
The present invention has been made in consideration of the above problems. It is accordingly an object of the present invention to provide an optical semiconductor device as a photocoupler having a chip structure in small size, and a method of manufacturing the same.
Another object of the present invention is to provide an optical semiconductor device with high efficiency of photocoupling, and a method of manufacturing the same.
Still another object thereof is to provide an optical semiconductor device, a plurality of which can be mounted with high density, and method of manufacturing the same.
In order to achieve the above objects, an optical semiconductor device may comprising:
a substrate having an opening, in a form of container;
a conductive layer for substrate which is formed on a bottom surface of the substrate;
a plurality of external electrodes which are formed on an external surface of the substrate and to be clerically connected to an external circuit;
a light emitting device or photodetector which is mounted on the conductive layer for substrate and electrically connected to the conductive layer and the external electrodes;
a cap which is fixed to the opening of the substrate;
a conductive layer for cap which is formed on a surface facing the light emitting device or photodetector; and
a photodetector or light emitting device, which is mounted on the conductive layer for cap, and electrically connected the conductive layer for cap and the plurality of external electrodes, and which faces the light emitting device or photodetector mounted on the substrate.
In the optical semiconductor device, a space throughout the substrate and the cap may be filed with a translucent resin.
A through hole for substrate, for connecting the conductive layer for substrate and the plurality of external electrodes, may be formed in the substrate; and
the through hole may be filled with a conductive material.
Further, a through hole for cap, for connecting the conductive layer for cap and the plurality of electrodes, may be formed in the substrate; and
the through hole for cap may be filled with a conductive material.
The substrate may comprise a bottom section and a side wall arranged on a peripheral section of the bottom section; and
the plurality of external electrodes may be formed on the bottom surface of the substrate.
The cap may comprise a flat surface section and a side surface section;
the plurality of external electrodes may be arranged on the side wall section of the substrate and on the side surface section.
The substrate may have a multi-layer structure;
a first conductive layer may be formed on a predetermined layer of the substrate;
the light emitting device or photodetector may be formed on the first conductive layer;
a second conductive layer may be formed on a layer being at a same height as a height of a surface of the light emitting device or photodetector formed on the first conductive layer; and
the light emitting device or photodetector and the second conductive layer may electrically he connected with each other through a bonding wire.
The plurality of external electrodes may be formed on the external surface of the substrate and on an external surface of the cap;
the plurality of external electrodes which are formed on the external surface of the substrate, and the plurality of external electrodes which are formed on the external surface of the cap may be arranged on a same plane;
the plurality of external electrodes which are formed on the external surface of the substrate may electrically be connected to the light emitting device or photodetector on the conductive layer for substrate; and
the plurality of external electrodes which are formed on the external surface of the cap may electrically be connected to the photodetector or light emitting device on the conductive layer for cap.
An optical semiconductor device according to the second aspect of the present invention may comprise:
a wiring substrate, on which a conductive layer for substrate having a predetermined wiring pattern is formed, and which has a plurality of openings in predetermined positions;
a plurality of external electrodes which art formed on an external surface of the wiring substrate and to be electrically connected to an external circuit;
a light emitting device or photodetector which is mounted on the conductive layer for substrate and electrically connected to the conductive layer and the external electrodes;
a cap which is fixed to each of the openings of the substrate;
a conductive layer for cap which is formed on E surface facing the light emitting device or photodetector; and
a photodetector or light emitting device, which is mounted on the conductive layer for cap, and electrically connected to the conductive layer for cap and the plurality of external electrodes, and which faces the light emitting device or photodetector mounted on the substrate.
In the optical semiconductor device, a space throughout the each of the plurality of openings and the cap may be filled with a translucent resin.
A through hole for substrate, for connecting the conductive layer for substrate and the plurality of external electrodes, may be formed in the substrate; and
the through hole may be filled with a conductive material.
In the optical semiconductor device, a through hole for cap, for connecting the conductive layer for cap and the plurality of electrodes, may be formed in the substrate; and
the through hole for cap may be filled with a conductive material.
The substrate may have a multi-layer structure;
a first conductive layer may be formed on a predetermined layer of the substrate;
the light emitting device or photodetector may be formed on the first conductive layer;
a second conductive layer may be formed on a layer being at a same height as a height of a surface of the light emitting device or photodetector formed on the first conductive layer; and
the light emitting device or photodetector and the second conductive layer may electrically be connected through a bonding wire.
A method of manufacturing an optical semiconductor device according to the third aspect of the present invention may comprise:
forming a conductive layer on a bottom surface of a substrate, having an opening, in a form of container;
forming a plurality of external electrodes, which are to be electrically connected to an external circuit, on the external surface of the substrate;
mounting a light emitting device or photodetector on the conductive layer for substrate, and electrically connecting the conductive layer for substrate with the plurality of external electrodes;
forming a conductive layer for cap on one surface, facing the light emitting device or photodetector, of a cap fixed to the opening of the substrate;
mounting a photodetector or light emitting device facing the light emitting device or photodetector on the conductive layer for cap, and electrically connecting the photodetector or light emitting device with the conductive layer for cap; and
attaching the cap to the opening of the substrate, and electrically connecting the photodetector or light emitting device mounted on the cap with the plurality of external electrodes.
The method of manufacturing an optical semiconductor device may comprise filling the opening of the substrate with a translucent resin, attaching the cap to the opening of the substrate with the translucent resin, and electrically connecting the photodetector or light emitting device mounted on the cap with the plurality of external electrodes, after the electrically connecting the conductive layer for substrate and the plurality of external electrodes.
The electrically connecting the conductive layer for substrate and the plurality of external electrodes may include:
forming a through hole for substrate, in the substrate, for electrically connecting the conductive layer for substrate with the plurality of external electrodes; and
filling the through hole for substrate with a conductive material.
The electrically connecting the photodetector or light emitting device with the plurality of external electrodes may include:
forming a through hole for cap, in the substrate, for electrically connecting the conductive layer for cap and the plurality of external electrodes; and
filling the through hole for cap with a conductive material.
The method of manufacturing an optical semiconductor device, may comprise:
forming the plurality of external electrodes on the external surface of the substrate;
electrically connecting the plurality of external electrodes formed on an external surface of the substrate with the light emitting device or photodetector on the conductive layer for substrate; and
forming the plurality of external electrodes on the external surface of the cap;
electrically connecting the plurality of electrodes formed on the external surface of the cap with the photodetector or light emitting device on the conductive layer for cap; and
attaching the external surface of the substrate, on which the plurality of electrodes are formed, to the external surface of the cap, on which the plurality of electrodes are formed, so that the external surface of the substrate and the external surface of the cap are formed on one surface of the optical semiconductor device.
A method of manufacturing an optical semiconductor device, according to the fourth aspect of the present invention may comprising:
forming, on a bottom surface of a wiring substrate, a conductive layer for substrate having a predetermined wiring pattern;
forming a plurality of openings in predetermined positions of the wiring substrate;
forming, on an external surface of the wiring substrate, a plurality of external electrodes which are to be electrically connected to an external circuit;
mounting a light emitting device or photodetector in each of the plurality of openings, and electrically connecting the conductive layer for substrate with the plurality of external electrodes;
forming a conductive layer for cap on a surface, facing the light emitting device or photodetector, of a cap which is fixed onto each of the plurality of openings;
mounting a photodetector or light emitting device facing the light emitting device or photodetector on the conductive layer for cap, and electrically connecting the photodetector or light emitting device with the conductive layer for cap; and
attaching the cap to each of the plurality of openings, and electrically connecting the photodetector or light emitting device mounted on the cap with the plurality of external electrodes.
The method of manufacturing an optical semiconductor device, may comprise filling each of the plurality of openings with a translucent resin, attaching the cap to each of the plurality of openings with the translucent resin, and electrically connecting the photodetector or light emitting device mounted on the cap with the plurality of external electrodes, after the electrically connecting the conductive layer with the plurality of external electrodes.
The electrically connecting the conductive layer with the plurality of external electrodes may include:
forming a through hole for substrate, in the wiring substrate, for electrically connecting the conductive layer for substrate with the plurality of external electrodes.
The electrically connecting the photodetector or light emitting device with the plurality of external electrodes may include:
forming a through hole for cap, in the wiring substrate, for electrically connecting the conductive layer for cap with the plurality of external electrodes; and
filling the through hole for cap with a conductive material.